[FEATURE] Create BE-user in Install Tool with a salted password

Introduce the possibility to salt the password when creating
a new Backend User in the Install Tool. When Saltedpasswords
is installed and backend usage is enabled the password will
be salted with saltedpasswords. Otherwise the md5 hashing method
is still used.

Change-Id: I30b2fab2c4158c878e849f061f0d464b501b62bc
Resolves: #31407
Releases: 6.2
Reviewed-on: https://review.typo3.org/22676
Reviewed-by: Nicole Cordes
Tested-by: Nicole Cordes